(a) Field of the Invention
The present invention relates to an improved structure of a pressure regulator, and more particularly to a pressure retractable tube construction, in which the elasticity of the coordination between the elasticity of the retractable tube and the pressure of a high pressure gas is utilized to achieve stable and pressure secondary pressure output without being affected by the primary pressure. Besides, leakage proof is ensured.
(b) Description of the Prior Art
Some gases, such as oxygen, acetylene, nitrogen, argon, etc., have to be containerized under high pressure so that they can be utilizable by industries. But before the gas can be output for use, the pressure of the gas must be adjusted to a suitable value by using a pressure regulator so as to ensure normal and safe operation of instrument pipelines, apparatus, or relevant equipment. And the major function of the pressure regulator is to ensure the stability of the output pressure.
FIGS. 1-4 show a conventional pressure regulator. A body 1 has an upper cover 11 screwably provided thereon and an interior divided into a primary pressure chamber P1 and a secondary pressure chamber P2. The primary pressure chamber P1 communicates with an intake duct 12 and a primary pressure gauge 13. The secondary pressure chamber P2 communicates with a discharge duct 14, a secondary pressure gauge 13, and a relief valve 16. A valve 17 having a small spring fitted at a bottom end thereof is disposed between the primary and secondary pressure chambers P1, P2 to control opening and closing of the path. Furthermore, the center of the upper cover 11 forms a recess 111, and a lower end thereof forms a flange 112 that, together with the body 1, keeps a plastic film 18 sandwiched therebetween so as to link-up with the valve 17 and partition the secondary pressure chamber P2 and the recess 111. The upper cover 11 is further provided with a threaded through hole at a top end thereof for mounting an adjusting screw 113 that extends into the recess 111. The recess 11 internally accommodates a large spring 19 that has an upper end provided with a packing plate 191 adapted to be urged against by the adjusting screw 113, and a lower end urging against a metal packing plate 181 provided at the center of the plastic film 18.
However, since the adjustment of the pressure in the secondary pressure chamber P2 is through the adjusting screw 113 that is disposed in a knob 114 and adjusts the position of the large spring 19 so that it exerts pressure a curved position of the plastic film 18 to thereby control the opening of the valve 17 to form a path and control the high pressure gas flowing from the primary pressure chamber P1 to the secondary pressure chamber P2. When the gas pressure of the secondary pressure chamber P2 is greater than the pressure exerted by the large spring 19 above the plastic film 18, the plastic film 18 will curve in deformation as shown in FIG. 4. At this time, the valve 17 is subjected to the elasticity of the small spring 171 at the bottom end and elevates to close the valve port 172 of the primary pressure chamber P1. When the discharge duct 14 releases pressure, the pressure in the secondary pressure chamber P2 drops, and the plastic film 18 will be subjected to the elasticity of the large spring 19 to resume its original curved shape, as shown in FIG. 3. Additionally, the metal packing plate 181 at the center of the plastic film 18 urges against a top rod 173 of the valve 17 to cause it to drop therewith, thereby opening the valve port 172, so that the gas in the primary pressure chamber P1 flows into the secondary pressure chamber P2. The pressure of the secondary pressure chamber P2 is continuously adjusted in the above manner to achieve the required pressure output.
Therefore, the plastic film 18 is constantly changing its curved shape. And because it has extendibility, after use thereof for a period of time, the plastic film 18 will be worn out. If the container is used to hold a corrosive gas, gas leakage may occur due to wearing out of the plastic film 18. In addition, the thickness of the plastic film 18 is not very uniform so that deformation often occurs at the relatively thin portions, and the force bearing area will likewise be affected.
Furthermore, since the output of the secondary pressure is achieved by using the adjusting screw 113 of the knob 114, the large spring 19, and the metal packing plate 181 to control the plastic film 18, the plastic film 18 cannot be positively controlled at a determined position. In addition, the high pressure gas in the steel cylinder will change with use. For instance, the pressure of the high pressure gas in the steel cylinder when full is about 150 kg/cm.sup.2, but there may remain only about 10 kg/cm.sup.2. Such a considerable pressure difference will cause the output pressure from the primary pressure chamber P1 to be unstable. As a result, the valve 17 located in the primary pressure chamber P1 and the small spring 171 at its bottom portion are likely to be affected by the pressure difference. Besides, since the small spring 171 controlling the elevation of the valve 17 has low elasticity, the influence on the valve 17 due to pressure difference is relatively greater, hence affecting the precision of the valve in gas flow control. Besides, the plastic film 18 that is flexible will also vibrate and deform in shape due to negative pressure and unstable pressure.